Know all about Siltstone and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Siltstone belongs to Sedimentary Rocks while Obsidian belongs to Igneous Rocks.Texture of Siltstone is Clastic whereas that of Obsidian is Glassy. Siltstone appears Rough and Obsidian appears Shiny. The luster of Siltstone is dull while that of Obsidian is vitreous. Siltstone is available in brown, red, reddish brown colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Siltstone are raw material for the manufacture of mortar, soil conditioner and that of Obsidian are creating artwork, mirror, used in aquariums.